Reducing noise that may be heard by vehicle occupants is desirable to automotive manufacturers. The reduction in noise emanating from vehicle air induction systems has been accomplished through the application of specific technology to vehicles. One type of technology provides frequency cancellation through the application of components such as resonators, quarter wave tuners, non-reflective inlet ducts, expansion chambers, or diffusers, to the vehicle. These components are applied at various locations throughout the air induction system, for example, with certain limitations. As one example of these limitations, the clean air intake duct must remain sealed between the air cleaner box and the throttle inlet.
Diffusers and non-reflective ducts that have openings to the atmosphere are not available for installation in the clean air intake duct between the air cleaner box and the throttle inlet. Therefore, clean air duct tuning must be accomplished using resonators, expansion chambers, or quarter wave tuners. Each of these components requires additional packaging space in the engine compartment of the vehicle. It is desirable to provide acoustic tuning of the inlet duct without the use of additional components.